Quantum dots (QDs), also referred to as nanocrystals, are nanoparticles composed of group II-VI element or group III-V element. The particle size of the QDs is generally between 1 and 20 nm. As electrons and holes are subjected to quantum confinement, continuous energy band structures are converted into discrete energy level structures, and hence the QDs can emit fluorescent light after excitation.
The emission spectrum of QDs may be controlled by the variation of the size of QDs. The emission spectrum of QDs may cover the entire visible light spectrum by the variation of the size and the chemical composition of QDs. Taking CdTe QDs as an example, when the particle size of the QDs is increased from 2.5 nm to 4.0 nm, the emission wavelength of the QDs can be changed from 510 nm to 660 nm.
Currently, the QDs may be used as molecular probes and applied to fluorescent labels and also may be applied to display devices by means of the emission characteristic of the QDs. When monochromatic QDs are used for a light source of a backlight module of an LCD, the monochromatic QDs are excited by a blue-light light-emitting diode (LED) and emit white ambient light formed by the mixture of monochromatic light and blue light. The resultant light has a larger color gamut, so that the image quality can be improved.
A current LCD has relatively low display brightness in the situation of intense outdoor light when applied to outdoor display, and hence the viewing effect can be affected. In general, the transflective display mode can be adopted to brighten the LCD. However, the aperture ratio of pixel units in the LCD can be reduced when the transflective display mode is adopted.